Friday, July 18, 2008

I wrote a blog article last year on why hedging isn't always better. The more I try to practice what I preached, the more I am convinced that most of the time, we are hedging the wrong risks.

Hedging should not be about reducing volatility in our portfolio. If reducing overall volatility is our goal, we should simply reduce leverage, as I have argued in my previous article. If volatility in a particular industry group is too much for us, (banks? brokerages? energy stocks?), just reduce the capital allocation in that group.

Sure, if hedging does increase your overall Sharpe ratio, go ahead and hedge to your heart's content. Kelly's formula tells us that the higher the Sharpe ratio, the higher the compounded growth rate of your wealth. The problem is, many of us hedge even when doing so do not clearly increase Sharpe ratio. A further problem is that we can achieve this maximum growth rate only if we use the high leverage recommended by Kelly's formula, but this leverage often exceeds what our brokerage would allow us. It is not clear that it is beneficial to waste our buying power on the hedge if we can only operate at sub-optimal leverage.

To me, hedging should be about eliminating the risk of ruin (equity reduced to zero) due to unexpected, catastrophic events. (Many sophisticated hedge fund managers cannot even meet this simple survival criterion, giving lie to the whole notion of "hedge" funds.)

For instance, let's assume that the worst one-day drop in the market index can be 20%. Furthermore, let's assume that you are able to endure a 30% reduction in equity during one trading period. Then you should not be afraid to have a net long exposure of 150% of your equity. In other words, not only should you not hedge, but you should go ahead and leverage your long-only portfolio 1.5 times.

I believe this notion of hedging, or buying insurance, extends to all spheres of our lives. We should avoid ruin, not mere losses. Otherwise, you will be paying too much on the insurance policy over the long term. In other words, max out the deductible on your insurance policy!